Questions about Cargo Trailers behind RV

Had to replace a rear brake light on it this afternoon, weird attachment, rubber grommet holding the whole light assembly in. Just pushed on it a little and it just popped right out. Assembly and me perplexed how to change the bulb. Didn't seem any way of opening it without breaking the housing. Fred Meyer had the same size assembly with LED bulbs. Just cut the old ones off and crimped on a new set. Wouldn't you know, one side had about 4' of extra wire, the other side had to reach inside to access wires. Thinking of a dab of silicon sealant around the edges to weather seal a bit more, there was some corrosion under the grommet. New license plate, all the standardized mounting holes were stripped out, Previous owner had drilled new holes in the plate, didn't have a drill with me. It's safety wired onto the rear door until I can find a better solution.